LED lamps are being developed by various companies for replacing fluorescent lamps in fluorescent lamp fixtures (“FLFs”). In many cases, the fluorescent lamp ballasts are removed or disconnected from a FLF, and additional wiring is provided to drive (or power) the LED lamps. In some cases, the LED lamps can be made to accept the electrical power input from a specific type of existing fluorescent tube ballast in the FLF. An economical option for fluorescent lamp replacement by an LED lamp is to leave the existing fluorescent lamp ballast in the FLF and to utilize such ballast for powering the LED lamps without any rewiring of the FLF.
As discovered by the present inventor, current LED lamp drive circuitry encounters a problem with three-wire magnetic ballasts used in fluorescent lamp fixtures (“FLFs”). Three-wire magnetic ballasts exhibit a high power factor when powering fluorescent lamps, but when powering LED lamps with a power factor corrected LED driver, the present inventor discovered that power factor substantially decreases to about 0.63, for instance. As is known, the power factor of an electrical circuit is the ratio of the real power flowing to the circuit to the apparent power in the circuit.
Accordingly, it would be desirable to provide an LED lamp system designed to fit into a fluorescent lamp fixture and which can utilize an existing three-wire magnetic fluorescent lamp ballast already present in the fluorescent lamp fixture, while presenting a power factor to AC mains of at least about 0.8.